Estimation of mesoscale strain with fatigue crack propagation through quantitative analysis of displacement vector fields by a television-optical measuring complex

In the work, a computational algorithm for crack opening through surface image processing of loaded materials in fatigue fracture was developed and studied in experiment. In the first part of the paper we analyze model displacement fields to test and verify the proposed procedure and software, and in the second part, we consider experimentally taken images of surface regions with a propagating fatigue crack. It is shown that for experimental study of fatigue fracture, it is appropriate to use two parameters: the average crack opening displacement and the shear strain intensity around the crack tip. Analysis of images containing both a deformation zone and an opening crack reveals a nonlinear dependence of the crack opening displacement on the shear strain intensity and this suggests that the computation domain fails to cover the entire strain localization zone.